1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to wireless telecommunications, and more particularly to a stored transmission packet having a structure intended to for use in a new link-adaption mechanism, and transmitting the transmission packet.
2. Description of the Related Art
In line with the increase in wireless network use and demand in mass data transmission, research on efficient transmission methods is desired.
Moreover, there is great demand for wireless transmissions of high quality video images such as digital video disk (DVD) and high definition television (HDTV) images to a variety of home devices.
Currently, one of the IEEE 802.15.3c task groups is establishing the technical standard for the transmission of mass data in a wireless home network. This standard, called Millimeter (mm) Wave, uses radio waves having millimeter wavelengths, i.e., a frequency in the range of 30 GHz to 300 GHz in order to transmit the mass data. This frequency range is unlicensed, and thus its use has been limited to telecommunication services, radio astronomy, and the prevention of automotive collisions.
FIG. 1 is a drawing illustrating a comparison between the IEEE 802.11 standard frequency band and that of mmWave. IEEE 802.11b and IEEE 802.11g have a carrier frequency of 2.4 GHz and a bandwidth of 20 MHz. In addition, IEEE 802.11a and IEEE 802.11n have a carrier frequency of 5 GHz and a bandwidth of 20 MHz. Conversely, mmWave has a carrier frequency of 60 GHz, and a bandwidth in the range of 0.5 to 2.5 GHz. Hence, mmWave uses a higher frequency band and a wider bandwidth than conventional IEEE 802.11 standards. As mentioned above, using high frequency signals (mmWave), data can be transmitted at a high rate (Gbps), and the size of an antenna can be set to 1.5 mm or less, thereby allowing the antenna to be included in a single chip. In addition, using high frequency signals, interference among the devices can be reduced due to the high attenuation ratio in air.
Recently, research on transmitting uncompressed audio or video data (hereinafter, referred to as “AV data”) among wireless devices using the high frequency band of mmWave. AV data is compressed by removing portions which humans are less sensitive to through motion compensation, DCT conversion, quantization, variable length coding, but uncompressed AV data includes unmodified digital values denoting pixel elements (i.e., R, G, and B).
Accordingly, bits included in the compressed AV data are equally significant, whereas bits included in the uncompressed AV data are not. For example, referring to FIG. 2, a pixel component is represented as 8 bits in the case of an 8-bit image. The bit with the highest degree (the highest-level bit) is the most significant bit (MSB), and the bit with the lowest degree (the lowest-level bit) is the least significant bit (LSB). That is, each bit of 1-byte data has a different significance when restoring audio signals. When an error occurs in the most significant bit during transmission, it is easier to detect the error than when it occurs in other bits. Accordingly, compared to the bit data with less significance, the bit data with more significance should be protected to prevent the error from occurring during wireless transmission. However, the conventional IEEE 802.11 standards use an error-correction method or a retransmission method in which all bits have the same coding rate.
FIG. 3 is a drawing illustrating a configuration of the IEEE 802.11a physical protocol data unit (PPDU). A PPDU 30 includes a preamble, a signal field, and a data field. The preamble is used for the synchronization of a PHY layer and channel estimations, including a plurality of short training signals and long training signals. The signal field includes a “RATE” field that indicates a transmission rate and a “LENGTH” field that indicates the length of the PPDU. Generally, the signal field is coded by a symbol. The data field comprises a physical layer service data unit (PSDU), a tail bit, and a pad bit and the data to-be-transmitted is included in the PSDU.
A link adaptation mechanism, used to selectively adapt to an ever-changing channel state, exits between a transmitter that transmits uncompressed AV data and a receiver that receives the uncompressed AV data. A link is adapted according to a transfer environment by adjusting parameters such as a data rate, a transmission-frame size, and transmitter/receiver power.
However, the starting point and execution method thereof are dependent on the number of valid ACK frames in the current link-adaptation mechanism, which renders the mechanism dependent on a reverse channel state where the data is transferred from a sink device to a source device as opposed to a forward channel state where the data is transferred from the source device to the sink device. Accordingly, it is unable to execute a smooth link-adaptation mechanism.